Then, section 3 provides a high level description of the assignment problem that DSA technique is applied to, while in section 4 several DSA algorithms are presented and described. The proposed RRM scheme for OFDMA-based networks is presented first. The rest of this paper is structured as follows. Framed within the above, this paper introduces an efficient RRM scheme which incorporates DSA algorithms that consider at the same time all the available management information, namely Context, Profiles and Policies in order to introduce fairness in the way that the sub-carriers are assigned to users, as well as to increase the overall system performance by utilizing the available spectrum only where and when it is necessary. To this context, RRM optimization functionalities which are responsible to find the most appropriate decisions in terms of feasibility, effectiveness and cost of radio resource usage must be also aware of other higher-level, but still critical information, like user requested services, user profiles and NOs policies. In order to achieve this target, advanced management functionalities that take into account network management level information in the context of RRM are more than necessary. Furthermore, Network Operator (NO) aim at providing network services to the users at the best possible QoS level and in the most cost-efficient manner. In this paper, we will focus on DSA algorithms and try to exploit their results towards proposing an efficient RRM scheme for OFDMA-based wireless networks. Finally, the transmitter can utilize AM in order to be able to transmit at higher data rates over the sub-carriers which exhibit better channel conditions, thus ensuring an acceptable Bit Error Rate (BER) in all sub-carriers. APA is responsible to find the optimum power allocation for the users’ sub-carriers in order to address issues of efficient frequency reuse and interference minimization. The target of DSA is to find the optimum number of sub-carriers to assign to each user so as they can be served with the maximum possible QoS level. In the context of Radio Resource Management (RRM) in OFDMA-based systems several techniques are provided and aim at addressing the problems of the versatile and highly varying, modern service area in a dynamic manner and by utilizing solutions for radio network adaptation namely, Dynamic Sub-carrier Assignment (DSA), Adaptive Power Allocation (APA) and Adaptive Modulation (AM), capable to address problems of the service area and provide solutions for proper network adaptation. Apart from such an inherently robust physical layer-related technique, proper Radio Resource Management (RRM) mechanisms are needed in order to increase performance in terms of spectral efficiency.
At the same time, OFDM has been proven to comprise a powerful and spectrum-efficient transmission scheme based on the principle of transmitting simultaneously many narrow-band frequencies (subcarriers), which are orthogonal to each other thus eliminating the interference between channels. OFDMA actually extends the Orthogonal Frequency Division Multiplexing (OFDM) transmission scheme for supporting multi-user applications. Orthogonal Frequency Division Multiple Access (OFDMA) is today adopted as the multiple access technology from many of the above mentioned RATs including e.g. The B3G concept dictates that Network Operators (NOs) will own heterogeneous infrastructures and will rely on different RATs, in order to satisfy stringent user and service requirements, often under difficult environment conditions. Moreover, the wireless world migrates towards the era of B3G (Beyond the 3rd Generation) communications (). Networks – WMANs (IEEE 802.16 family - WiMAX).
0 kommentar(er)
